Unit 6 ( CONSTRUCTION OF THE FLEXIBLE PAVEMENT )

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CONSTRUCTION OF THE FLEXIBLE

PAVEMENT

OBJECTIVES

General Objective

To understand general items of flexible pavement constructions. To understand general items of flexible pavement constructions.

Specific Objectives

At the end of the unit you should be able At the end of the unit you should be able

to:-•

• identify the structural element of flexible pavement.identify the structural element of flexible pavement. •

• describe the functions of each layer in flexible pavement.describe the functions of each layer in flexible pavement. •

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CONSTRUCTION OF THE CONSTRUCTION OF THE

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6.

6.0 0 ININTRTRODODUCUCTITIONON

The pavement is the hardest layer of the road structure. It does not The pavement is the hardest layer of the road structure. It does not

include the side walk of the road. Its location is on the ground formation on include the side walk of the road. Its location is on the ground formation on sub-grade. It is away of traffic. The nature of the soil is usually not strong enough to grade. It is away of traffic. The nature of the soil is usually not strong enough to stand the weight of the heavy vehicles and does not have a balanced surface. stand the weight of the heavy vehicles and does not have a balanced surface. That is why the pavement layer should be constructed on original ground surface That is why the pavement layer should be constructed on original ground surface so that the force can be divided equally. This is to ensure that road user will have so that the force can be divided equally. This is to ensure that road user will have a save and comfortable journey. There are two types of pavement, namely

a save and comfortable journey. There are two types of pavement, namely Flexible Pavement and Rigid Pavement.

Flexible Pavement and Rigid Pavement.

STRUCTURE OF FLEXIBLE PAVEMENT STRUCTURE OF FLEXIBLE PAVEMENT

Flexible pavement is any kind of pavement that is not constructed using Flexible pavement is any kind of pavement that is not constructed using concrete. In Malaysia the pavement is commonly, constructed by using flexible concrete. In Malaysia the pavement is commonly, constructed by using flexible pavement. Pavements with very low flexural strength and are flexible in their pavement. Pavements with very low flexural strength and are flexible in their structural behaviour when under a load are called flexible pavements. The layers structural behaviour when under a load are called flexible pavements. The layers of this type of pavement reflect the deformation of the lower layers that are

of this type of pavement reflect the deformation of the lower layers that are

INPUT

CONSTRUCTION OF THE FLEXIBLE

PAVEMENT

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C3010 / UNIT C3010 / UNIT 66 The structure of the road mainly consists of the following layers.

The structure of the road mainly consists of the following layers. ii.. SSuubb--ggrraadde e ssooiil l oor r ssiimmpplly y ssuubb--ggrraaddee..

iiii.. SSuubb--bbaassee.. iiiiii.. RRooaad d BBaassee.. iivv.. SSuurrffaacce e llaayyeerr..

figure 6.1 figure 6.1

6.2

6.2 FUNFUNCTICTIONS ONS OF OF FLEFLEXIBLXIBLE E PAVPAVEMEEMENTNT 6.2.

6.2.1 1 SUBSUB-GR-GRADEADE

Sub-grade is a layer of natural soil or filled soil, ready to receive the Sub-grade is a layer of natural soil or filled soil, ready to receive the pavement material over it. Traffic load moving on the surface of the road is pavement material over it. Traffic load moving on the surface of the road is ultimately transferred to the grade through intermediate layer of ultimately transferred to the grade through intermediate layer of sub-base, base and surface layer. For the success full construction of the base, base and surface layer. For the success full construction of the road, it is necessary that the soil sub-grade should never be over road, it is necessary that the soil sub-grade should never be over

stressed. Stress intensity on the sub-grade should not be of the magnitude stressed. Stress intensity on the sub-grade should not be of the magnitude that may cause excessive deformation in the sub-grade. It is this reason that may cause excessive deformation in the sub-grade. It is this reason that the strength properties of the soil sub-grade should be evaluated. The that the strength properties of the soil sub-grade should be evaluated. The

Construction Depth Construction Depth Surface layer Surface layer Road Base Road Base Sub-base Sub-base

Sub-grade is the natural Sub-grade is the natural

soil beneath road soil beneath road

construction construction

Figure 6.1 Figure 6.1

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C3010 / UNIT C3010 / UNIT 66 expected ones, it is given suitable treatment to impart improvement in its expected ones, it is given suitable treatment to impart improvement in its performance.

performance.

There are a number of tests which can be used to measure There are a number of tests which can be used to measure

strength properties of the soil sub-grade. All these tests are empirical and strength properties of the soil sub-grade. All these tests are empirical and are useful in their correlation in the design. Following are some of the are useful in their correlation in the design. Following are some of the standard tests, used to evaluate the strength properties of the soil. standard tests, used to evaluate the strength properties of the soil.

1

1.. CC..BB..R R tteesstt 2.

2. PlPlatate bee beararining teg testst 3.

3. TrTriaxiaxial cial comomprepressssion tion testest SUB-BASE

SUB-BASE

Sub-base is one course that is constructed with quality materials. Sub-base is one course that is constructed with quality materials. This is the lowest layer of pavement that is constructed onto the This is the lowest layer of pavement that is constructed onto the sub-grade. The functions of sub-grade:

grade. The functions of sub-grade: •

• Support the road base and spreads the force to the sub-grade.Support the road base and spreads the force to the sub-grade. •

• Prepares the drainage using rough materials.Prepares the drainage using rough materials. •

• Prepares a cover at any layer that is constructed.Prepares a cover at any layer that is constructed. •

• Bears the pressure from heavy vehicles so the sub-grade will notBears the pressure from heavy vehicles so the sub-grade will not crack.

crack. •

• Prevent the sub-grade from traffic flow.Prevent the sub-grade from traffic flow.

BASE BASE

Base or road base is the main course to absorb force from surface Base or road base is the main course to absorb force from surface directly and spread the force to the thickest layer. This layer is normally directly and spread the force to the thickest layer. This layer is normally made from broken stones which may be bounded or unbounded. It is used made from broken stones which may be bounded or unbounded. It is used

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C3010 / UNIT C3010 / UNIT 66 deformation caused by the consolidation of the sub-grade is prevented. deformation caused by the consolidation of the sub-grade is prevented. This layer is evaluated by plate bearing test or stabilometer test.

This layer is evaluated by plate bearing test or stabilometer test. SURFACE

SURFACE

The surface is the top layer in a pavement. The pavement is The surface is the top layer in a pavement. The pavement is

divided into two layers that is Base course and wearing course on the top. divided into two layers that is Base course and wearing course on the top.

a. Base Course a. Base Course

In resurfacing, this layer is usually known as a binder course. It is In resurfacing, this layer is usually known as a binder course. It is the second layer before the wearing course. The function is to the second layer before the wearing course. The function is to spread the force from the surface.

spread the force from the surface. b. Wearing Course

b. Wearing Course

The wearing course is the top most layers in a pavement. The The wearing course is the top most layers in a pavement. The functions of this layer are as follows:

functions of this layer are as follows: •

• Provides smooth and dense ridding surface.Provides smooth and dense ridding surface. •

• Takes up wear and tear due to traffic.Takes up wear and tear due to traffic. •

• Provides water tight surface against filtration of surfaceProvides water tight surface against filtration of surface water.

water. •

• Provides hard surface which can withstand the pressureProvides hard surface which can withstand the pressure exerted by tyres of vehicles.

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“WANT TO IMPROVE YOUR UNDERSTANDING? TRY THESE “WANT TO IMPROVE YOUR UNDERSTANDING? TRY THESE

ACTIVITIES AND GOOD LUCK!!!” ACTIVITIES AND GOOD LUCK!!!”

6.1

6.1 Label Label the the layers layers of of the the flexible flexible pavemenpavement t roads roads given given below.below.

6.2

6.2 Write Write down down the the short short notes notes about about the the functiofunctions ns of of each each layer layer of the flexible pavement.

of the flexible pavement.

ACTIVITY 6A

Construction Construction Depth Depth SURFACE_________________________________________ SURFACE_________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ ROAD BASE_______________________________________ ROAD BASE_______________________________________

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6.3

6.3 What What are are the the differendifferences ces between between base base course course and and wearinwearingg course in the surface layer?

course in the surface layer?

SUB GRADE_______________________________________ SUB GRADE_______________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ SUB BASE_________________________________________ SUB BASE_________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ SURFACE SURFACE LAYER LAYER Base Course Base Course ___________________ ___________________ ___________________ ___________________ Wearing Course Wearing Course ___________________ ___________________ ___________________ ___________________

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6.1 6.1 6.2 6.2

FEEDBACK ON

ACTIVITY 6A

Surface Surface Road Base Road Base Sub Base Sub Base Sub-grade Sub-grade Construction Construction Depth Depth SURFACE

SURFACE is the top layer of the road pavement. It provides ais the top layer of the road pavement. It provides a smooth and dense surface. It provides water tight surfaces smooth and dense surface. It provides water tight surfaces against filtration of surface water.

against filtration of surface water. ROAD BASE

ROAD BASE is the main course of the road pavement. Itis the main course of the road pavement. It absorbs force from surface directly and spreads the force to absorbs force from surface directly and spreads the force to SUB BASE

SUB BASE is one course that is constructed to prepare theis one course that is constructed to prepare the drainage from rough materials, and it absorbs forces from road drainage from rough materials, and it absorbs forces from road base directly and spreads the forces to the sub grade.

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6.3 6.3 SURFACESURFACE LAYER LAYER Base Course Base Course It is the second layer It is the second layer before wearing course. before wearing course.

Its function is to Its function is to spreads the force from spreads the force from the surface to the road the surface to the road

base. base.

Wearing Course Wearing Course It provides smooth and It provides smooth and dense riding surface. As dense riding surface. As a top course, it receives a top course, it receives

the traffic forces the traffic forces

directly. directly.

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C3010 / UNIT C3010 / UNIT 66 6.3

6.3 FLEFLEXIBLXIBLE E PAVPAVEMEEMENT NT CONCONSTRSTRUCTUCTION ION PROPROCESCESSS

6.3.1 6.3.1 PREPAR

PREPARATION SU

ATION SUB-GRADE

B-GRADE LAYER

LAYER

Prepare the sub-grade layer, it is done after placing the drainage Prepare the sub-grade layer, it is done after placing the drainage system, piping and electric cable. The sub-grade surface will be

system, piping and electric cable. The sub-grade surface will be compacted levelled and be cut

compacted levelled and be cut to make camber ato make camber as in plan. s in plan. If the materialIf the material of the soil did not have a good quality, it will be changed with suitable of the soil did not have a good quality, it will be changed with suitable material.

material.

Base formation covers with 50-75mm sand layer or quarry dust and Base formation covers with 50-75mm sand layer or quarry dust and will be compacted with 8-10 tone compactors. This job must be done to will be compacted with 8-10 tone compactors. This job must be done to prevent the clay from absorbing into the stone layer of sub-base and prevent the clay from absorbing into the stone layer of sub-base and reduce the shear strength of the pavement.

reduce the shear strength of the pavement.

6.3.2

6.3.2 CONSTRCONSTRUCTIOUCTION AND CON AND COMPACTMPACTING THE ING THE SUB-BASUB-BASESE

After the sub-base has been prepared with list materials, it will be After the sub-base has been prepared with list materials, it will be placed and constructed into two layers if the thickness is more then placed and constructed into two layers if the thickness is more then 150mm. Every layer will be compacted according to the plan. Sub-base 150mm. Every layer will be compacted according to the plan. Sub-base layer must be compacted carefully with compactor machine. Compactors layer must be compacted carefully with compactor machine. Compactors

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6.3.3

6.3.3 CONSTRCONSTRUCTIOUCTION ON OF RF ROAD OAD BASEBASE

Before road base is constructed, sub-grade surface and sub-base Before road base is constructed, sub-grade surface and sub-base must be formed perfectly and compacted enough. The lowest layer and must be formed perfectly and compacted enough. The lowest layer and sub-base must be prepared at least distance of 200m from the base sub-base must be prepared at least distance of 200m from the base construction.

construction.

The road base in Malaysia is commonly constructed with a material The road base in Malaysia is commonly constructed with a material known as crusher run. This material is place and compacted to on the known as crusher run. This material is place and compacted to on the surface of the road. The road base must be constructed in two layers of surface of the road. The road base must be constructed in two layers of same thickness. Each layer should not exceed 150mm.

same thickness. Each layer should not exceed 150mm.

6.3.4

6.3.4 CONSTRCONSTRUCTIOUCTION ON OF ROF ROAD SAD SURFACURFACEE

The road surface

The road surface is constructed with bitumen is constructed with bitumen materials, materials, such assuch as concrete asphalt, macadam bitumen and so on. The constructed should concrete asphalt, macadam bitumen and so on. The constructed should be free from dust and waterproof. To construct the surface layer, the base be free from dust and waterproof. To construct the surface layer, the base course must be prepared first. Prime coat is poured onto the road base course must be prepared first. Prime coat is poured onto the road base surface to be a binder between the road bases and the base course. To surface to be a binder between the road bases and the base course. To

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C3010 / UNIT C3010 / UNIT 66 The compacting must be done immediately. It should be compacted The compacting must be done immediately. It should be compacted from the side towards the middle of the road. It there is a super elevated from the side towards the middle of the road. It there is a super elevated bend, then it should be compacted from lower part to higher part. The type bend, then it should be compacted from lower part to higher part. The type of compactors must be according to the specifications.

of compactors must be according to the specifications.

Finally wearing course is prepared. Like always, base course Finally wearing course is prepared. Like always, base course

should be cleaned before tack coat is poured. The compacting job is done should be cleaned before tack coat is poured. The compacting job is done the same way as the base course.

the same way as the base course.

BITUMEN HAD BEEN BITUMEN HAD BEEN

PAVEMENT PAVEMENT HOPPER

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ACTIVITIES AND GOOD LUCK!!!” ACTIVITIES AND GOOD LUCK!!!”

6.4

6.4 CompComplete lete the the chachart rt by by fillfilling ing in in the the missmissing ing stagstages.es.

ACTIVITY 6

1.________________ 1.________________ _________________ _________________ _________________ _________________ _________________ _________________ 2. Constructing and 2. Constructing and compacting the sub compacting the sub base

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6.4 6.4

FEEDBACK ON

ACTIVITY 6

1. Preparing the 1. Preparing the sub-grade layer. grade layer. 4. Constructing the 4. Constructing the road surface. road surface. 3. Constructing the 3. Constructing the 2. Constructing and 2. Constructing and compacting the sub compacting the sub base.

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1.

1. Describe briefly the functions of flexible pavement by each layer.Describe briefly the functions of flexible pavement by each layer. 2.

2. The roaThe road surfacd surface is e is conconstrustructed witcted with bitumeh bitumen materin material. Descal. Describe the roaribe the roadd surface construction include the compaction work.

surface construction include the compaction work. 3.

3. State the functions of wearing course are as follows:State the functions of wearing course are as follows:

Question

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1.

SUB-GRADE SUB-GRADE

Sub-grade is a layer of natural soil or filled soil, ready to receive the Sub-grade is a layer of natural soil or filled soil, ready to receive the pavement material over it. Traffic load moving on the surface of the road is pavement material over it. Traffic load moving on the surface of the road is ultimately transferred to the grade through intermediate layer of ultimately transferred to the grade through intermediate layer of sub-base, base and surface layer. For the success full construction of the base, base and surface layer. For the success full construction of the

Answer

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C3010 / UNIT C3010 / UNIT 66 2.

2. PlPlatate bee beararining teg testst 3.

3. TrTriaxiaxial cial comomprepressssion tion testest SUB-BASE

SUB-BASE

Sub-base is one course that is constructed with quality materials. Sub-base is one course that is constructed with quality materials. This is the lowest layer of pavement that is constructed onto the This is the lowest layer of pavement that is constructed onto the sub-grade. The functions of sub-grade:

grade. The functions of sub-grade: •

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C3010 / UNIT C3010 / UNIT 66 force from the surface. The wearing course is the top most layers in a force from the surface. The wearing course is the top most layers in a pavement. The functions of this layer are as follows:

pavement. The functions of this layer are as follows: •

• Provides water tight surface against filtration of surfaceProvides water tight surface against filtration of surface water.

water. •

• Provides hard surface which can withstand the pressureProvides hard surface which can withstand the pressure exerted by tyres of vehicles.

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C3010 / UNIT C3010 / UNIT 66 Finally wearing course is prepared. Like always, base course Finally wearing course is prepared. Like always, base course should be cleaned before tack coat is poured. The compacting job should be cleaned before tack coat is poured. The compacting job is done the same way as the base course.

is done the same way as the base course.

3.

3. ThThe we weaeariring ng cocoururse se is is ththe te top op momost st lalayeyers rs in in a pa pavavememenent. t. ThThee functions of this layer are as follows:

functions of this layer are as follows: •